You may be aware that I have been doing quite a lot of experimenting with CFWA.

I'm using a Tokina 10-17, a Kenko 1.4 x teleconverter, and a Zen 100mm dome.

With larger subjects, like the sturgeon below, in green water and low light, I seem to be struggling to get the DOF sorted. To my eye, the snout is out of focus (and a little over exposed) Settings were 1/50th at f5, 200 ISO.

I want to expose for the background, which means an open aperture (and slow shutter speed) - which gives me a relatively shallow DOF. In this case, the Sturgeon's snout was almost on my dome!

I agree with Mike, try bumping the iso and adjusting the stop for DOF. I would also look to raise the strobes a hair. Looks like a little more light higher on the subject would be a little more pleasing.

I hesitate to (ever!) disagree with Alex, but I agree with others that I'd bump the ISO. The slight noise you might get should be far less noticeable/distracting than having the subject out of focus...and if you use Noise Ninja, you could make the noise scarcely noticeable at all.

In that light, unless you use your strobes to light the fish more, you've got limited ways to get enough light to get it exposed, sufficient DoF AND in sharp focus. I like the shot, but immediately noticed the blur...it could have been a great shot if it was more in focus.

Edited by bmyates, 19 March 2010 - 11:01 AM.

Bruce Yateswww.UnderwaterReflections.com
Lumix GX8 in Nauticam, Canon 5DMkII in Aquatica, 1DsMkII in Seacam, G15 in RecSea...Inon Z240's...too many lenses"If at first you don't succeed, try, try again. Then quit. No use being a damned fool about it." WC Fields

Adam, what was your shutter on the second photo? looks like it was far faster than the first shot. You need to concentrate on the shutter speed more for the background as opposed to the fstop. Raise the fstop to f8-11 for more DOF and lower the shutter speed for the background exposure.

Just a thought Adam.
Maybe another approach would be to put the Sturgeons snout and the eye in the same image plane, that way the most important parts of the photo would be sharp.
I believe Martin Edge calls it "paralleling the subject" in his book. Though he mentions it in connection with a flat port, I'm sure its the image plane that matters with regard to DOF.

The second image is 1/60th at f7.1. It was taken on a particularly gloomy day! Lovely British weather!

The point about paralleling the subject is a good one-in this instance though, and given the distance between the snout of the sturgeon and it's eye-unless you want a side on image, you are forced I think to try and increase DOF. The problem with CFWA is that the snout of the sturgeon is almost on the port in the first picture!

I do think that maybe working on placing the focus point may help. I must admit that I wasn't really concentrating on where it was.